Jason Alexander, as George Constanza, and Jerry Seinfeld (as himself) during their <i>Seinfeld</i> sitcom days.

Jason Alexander, as George Costanza, and Jerry Seinfeld (as himself) during their Seinfeld sitcom days.

Jerry Seinfeld has confirmed that a Seinfeld reunion is in the works and will happen "very, very soon".

The comedian was a guest on WFAN-TV's Boomer & Carton radio show, where he opened up about rumours surrounding a possible reunion of the hugely popular '90s sitcom.

Earlier this month, Seinfeld hinted at a "top-secret project" he and Seinfeld co-creator Larry David were working on during a Reddit AMA session. "We wrote this script for this thing that you will eventually see but I can't reveal what it is at this time," he wrote.

A week later, Seinfeld, David, and actor Jason Alexander, who played George Costanza in the show, were seen filming together at New York's iconic Tom's Restaurant, made famous by the sitcom.

Speaking on the radio show on Thursday, the comic confirmed that they weren't filming a Super Bowl advertisement or an episode of his popular web series Comedians in Cars Getting Coffee.

He added, ''I gave you more now than I've given anyone. I told you what it isn't, and then I also told you that it isn't not that either.''

The radio hosts continued to grill Seinfeld on his secret project in a casual game of ''20 questions''.

While Seinfeld was tight-lipped, he did reveal a few key details.

The project will be a "one-and-done" special, involve other Seinfeld characters, is "shortish'' but will be longer than 60 seconds, locations other than Tom's Restaurant will be used, but not Jerry's apartment, and it is coming "very, very soon".